Respiratory Syncytial Virus (RSV) is the most important viral agent causing acute lower respiratory infections in infants worldwide. Almost all children have been infected at the age of 3. Since it is a leading cause of hospitalization among infants, RSV represents a high burden on health care systems. It is also a cause of serious lower respiratory infections in immunocompromised and elderly adults.
Currently, there are only two approved drugs for use in patients having or at risk of having an RSV infection, namely ribavirin and palivizumab. No RSV vaccine is presently available for humans, and the complexity of the immune response to RSV infections coupled to the constraints imposed by pediatric applications render the development of an RSV vaccine particularly challenging.
Ribavirin is a nucleoside analog used for therapeutic intervention, especially for treating RSV infections in individuals at high risk for severe disease. However, ribavirin is non-specific to RSV. In addition, there is limited evidence of the actual benefits provided by ribavirin but increasing proofs of toxic and teratogenic properties of such compound. Consequently, the use of ribavirin is inacceptable particularly in infants and children.
Palivizumab is a humanized monoclonal antibody targeting the RSV fusion protein and is currently used for preventive purposes. Monthly prophylaxis with Palivizumab injections reduces RSV hospitalizations by approximatively 50%. However it is extremely expensive, and cost-benefit analyses showed to be mixed. Moreover, the type of administration is generally not acceptable for an infant population. Therefore, its current use is generally limited to high-risk pediatric patients.
There is thus an obvious and urgent need for a new therapeutic strategy for specifically targeting RSV with an improved efficiency.